The present invention relates to magnetic storage devices which use floppy record disks mounted in a cartridge. More particularly, this invention relates to the use of two or more magnetic floppy disks stabilized by a Bernoulli surface.
It is well known that a predictable and constant spacing between a record medium and a transducer is necessary in order to have successful magnetic retrieval and recording of data (i.e., read/write operation). One method of stabilizing the floppy disk is to rotate the disk at high speeds over a flat rigid plate, sometimes called a Bernoulli surface. In this way, an air bearing is created between the flexible magnetic disk and the rigid Bernoulli surface such that a constant and predictable spacing between the Bernoulli surface and the magnetic disk is established. Once the flexible magnetic disk is stabilized, the transducer can be brought into close proximity to the rotating disk at the proper distance from the disk surface. When a transducer "flies over" or is "coupled to" a magnetic disk, as those terms are used in the art, the transducer will penetrate or dimple the flexible medium. The distance between the record surface and the transducer surface can be precisely predicted when this dimpling phenomenon occurs. In this way, the floppy disk is stabilized by the Bernoulli surface and the spacing between the transducer and the disk surface can be precisely predicted and fixed.
It is desirable in the field of magnetic recording to achieve simultaneous access to two magnetic recording surfaces by two magnetic transducers. However, due to the dimpling of the magnetic medium as the transducer is flown in juxtaposition to the disk, it has not been possible to access both surfaces of the magnetic medium simultaneously when two transducers are substantially opposed to one another.
It has been shown in the prior art that two magnetic record surfaces can be accessed by two transducers by rotating each disk against a separate Bernoulli surface. See for example IBM Technical Disclosure Bulletin, Volume 19, No. 9 of February 1977. Another example of prior art which shows two magnetic disks accessed by two separate transducers is Russian Pat. No. 594527. However, in this disclosure three stabilizing surfaces are used: one below the bottom disk, one above the top disk, and a single stabilizing surface which is held between the disks in the region of the transducer.
A disadvantage of prior art attempts at accessing two magnetic surfaces simultaneously is that prior art applications are not practical in today's small and portable magnetic disk drive devices. As can be seen from the above cited references, the prior art frequently utilized separate actuators and Bernoulli surfaces for each magnetic surface. In other cases, large and complex means were used to stabilize two or more magnetic surfaces.